Safety pilot enclosure having flame-diverting air inlet

ABSTRACT

A gust-protecting safety pilot enclosure utilizes a hood which directs the pilot flame in two tongues, one of which heats a thermocouple within the enclosure and the other extends slantingly through the upper portion of the enclosure wall to ignite the main burner. A horizontal air flow opening in the enclosure wall beyond the thermocouple serves, when the pilot flame height is reduced, to divert a portion of the flame from the tongue which extends toward the thermocouple to the tongue which extends toward the main burner, thereby to prefer ignition of the main burner over voltage output from the thermocouple.

United States Patent [191 Koskolos 1 June 11, 1974 SAFETY PILOT ENCLOSURE HAVING FLAME-DIVERTING AIR INLET [75] Inventor: Nick J. Koskolos, Affton, Mo.

[73] Assignee: Intertherm, Inc., St. Louis, Mo.

[22] Filed: Apr. 23, 1973 [211 Appl. No.: 353,342

[52] US. Cl 431/350, 431/80, 431/347 [51] Int. Cl. F23d 15/04 [58] Field of Search 431/347, 350, 80; 239/103 [56] References Cited UNITED STATES PATENTS 3,173,472 3/1965 Loveland 431/80 3,405,999 10/1968 Riehl 431/350 X 3,692,016 9/1972 Stikkers et a1. 431/350 X 3,723,050 3/1973 Stevens et a1 431/350 X Primary Examiner-Edward G, Favors [5 7] ABSTRACT A gust-protecting safety pilot enclosure utilizes a hood which directs the pilot flame in two tongues, one of which heats a thermocouple within the enclosure and the other extends slantingly through the upper portion of the enclosure wall to ignite the main burner. A horizontal air flow opening in the enclosure wall beyond the thermocouple serves, when the pilot flame height is reduced, to divert a portion of the flame from the tongue which extends toward the thermocouple to the tongue which extends toward the main burner,

thereby to prefer ignition of the main burner over voltage output from the thermocouple.

7 Claims, 1 Drawing Figure SAFETY PILOT ENCLOSURE HAVING FLAME-DIVERTING AIR INLET BACKGROUND OF THE INVENTION Conventional safety pilots for gas-fired furnaces and other gas-fired appliances use a safety pilot which both ignites the gas from a main burner and provides heat to a thermocouple which controls a main shut-off valve. With one common type of pilot, the gas supplied to a pilot flame has no air intermixed with it. Instead gas is directed to impinge on a flame-developing hood which slants upwardly above it; surrounding air is here entrained and mixed into the gas, to support combustion. The hood may taper wideningly from a central hood indentation; the flame developed will then extend in a two-tongued fork, one of the tongues directed toward the thermocouple and the other extending angularly outward to ignite the main burner.

It is conventional to protect such pilots by enclosing them in rectangular sheet metal box-like shields, windowed to travel a portion of the pilot flame sideward for igniting the gas from a main burner orifice. The requirements that the pilot flame be shielded and that it light the main burner gas are somewhat conflicting.

One problem is how to assure an adequate voltage drop in the thermocouple output as the pilot flame lowers. A serious danger may arise when the pilot flame is substantially reduced, as happens when a particle of dirt or scale lodges in the pilot burner orifice. In such event the tongue of flame which heats the thermocouple may create a voltage output sufficient to hold open the pilot safety which controls the gas supply, while the tongue of flame directed toward the main burner orifice may be small. If, within four seconds after a switch opens the gas supply to the main burner, the gas flowing from it is not ignited by this second tongue, there may be a serious build-up of gas so that the delayed ignition which follows may be explosive. Accordingly, it is desirable to provide some means whereby, if the pilot flame height is reduced, part of the flame which remains should be diverted from the thermocouple to the main burner.

SUMMARY OF THE INVENTION The present invention uses a safety pilot including a conventional vertical pilot orifice, a vertical thermocouple spaced therefrom, and a slanting hood whose down-turned edges develop a two-tongued flame, to ignite the main burner and to heat the thermocouple controlling the gas supply shut-off valve. A new sheet metal enclosure is provided whose vertical side walls shield the pilot orifice and at least the lower portions of the hood and thermocouple from horizontal air flow. The side wall between the pilot flame and the main burner orifice has a laterally indented portion with a top edge cut-out through which one down-tumed edge of the slanting hood extends, so that the tongue of flame to the main burner may project between them. In an adjacent side wall adjacent to the thermocouple and remote from the pilot gas orifice, a horizontal air flow opening is provided at an elevation corresponding to the elevation within the hood at which the flame develops. If the pilot flame height lowers, air flowing through the horizontal air flow opening into the enclosure serves to cool the thermocouple and divert a portion 'of the flame from that tongue which extends toward the thermocoua pie to the other tongue which extends toward the main burner. This diversion of part of the flame toward the main burner favors ignition of the main burner over voltage output of the thermocouple. It offers some assurance that, as the flame height lowers, the thermocouple voltage output will drop as a sufficiently large tongue of flame is still directed toward the main burner. Hence the gas supply will be shut off before the ability of the pilot to ignite the main burner is seriously impaired.

BRIEF DESCRIPTION OF THE DRAWING The drawing is an enlarged perspective view, partly broken away, of a safety pilot assembly embodying the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The illustrated embodiment of the invention is adapted for use with gas furnaces such as used in mobile homes. A main gas manifold pipe a extends horizontally to a domed closed end b, near which it has a vertical tapped bore in which a main burner orifice c is screwed. As is conventional, gas to the manifold pipe a is supplied through a supply tube having an electromagnetic shut-off valve, not shown. The pipe a is welded to a welded bracket d for support, and is connected by a locating stud e to some structure of the furnace. The bracket d has a vertical plate f to which is attached the safety pilot assembly to be described.

The pilot enclosure of the present invention has an angular base bracket generally designated 10, including a vertical leg 11 screw-mounted onto the bracket plate f as hereinafter described and horizontal leg 12. The horizontal leg 12 is penetrated by two base couplings, one for a vertical thermocouple l4 and the other for a safety pilot generally designated 15. A conventional thermocouple connection 16 leads from the base of the thermocouple 14 to such electromagnetic shut-off valve for the gas manifold pipe a; the pilot gas supply tube 17 leads from the base of the pilot 15 to a gas sup ply source not shown. Except for the couplings to the thermocouple l4 and safety pilot 15, the horizontal base leg 12 of the bracket 10 is preferablyimperforate.

Secured onto the horizontal leg 12 above the coupling for the pilot gas supply tube 15 is a pedestal shield 20. It flares outwardly to a horizontal surface 21 and has a central bore 22 within which is mounted the base portion 23 of a hood generally designated 25. The lower portion of the hood is open, at the horizontal surface 21, opposite to the thennocouple l4, thereabove it flares wideningly outward and then slantingly upward. In its slant and angular position it is directed partly toward the thermocouple l4 and partly outward toward the gas orifice 0. Its flame-developing portion 26 tapers broadeningly to a tongue-developing portion 27, which has a broad central indented part 28 and two channel-like portions 29 flanked by downward presented edges 30 of the hood. As is known, such a hood will develop, at the flame-developing portion 26, a flame by entraining ambient air into the gas which impinges on it; the flame will divide in the tonguedeveloping portion 27 into two tongues which project through the channel-like portions 29 along and within the edges 30.

One of the tongues of flame so developed is directed toward the thermocouple 14, thus in a typical installation the thermocouple 14 will have a 30 mv. output when heated for a substantial period of time by a pilot flame of normal height; in starting its output must reach about 7 or 8 mv. to open the conventional electromagnetic shut-off valve. Such a shut-off valve will however tend to remain open, when the pilot flame is lowered, even when the thermocouple output is as little as approximately 3 mv. The other tongue of flame, which projects outward, serves to ignite the gas-air mixture above the main burner orifice when the gas supply is turned on, as by such conventional thermostat control, not shown. A problem of the invention is to shield the pilot flame from horizontal gusts, more effectively than with a conventional windowed enclosure, and yet permit this latter tongue of flame to travel toward and ignite gas from the main burner orifice c- In the present invention a sheet metal enclosure generally designated 33 is utilized. It may be formed of stainless steel to substantially rectangular cross-section, so as to fit fairly snugly about the horizontal leg 12 of the base bracket and extend thereabove to a height slightly less than that of the hood 25. At its upper end, the enclosure 33 has a horizontal lip 34 which extends over a portion of the hood 25 and a second horizontal lip 35, on the opposite side, which extends toward the thermocouple 14, leaving a top opening through which project the tip of the thermocouple l4 and the upper portion of the hood 25 as best seen in FIG. 2.

Beneath the lip 35, there is provided in the wall 36 adjacent to the thermocouple 14 a horizontal air inflow passage 37 whose diameter may be slightly greater than I that of the thermocouple.

. The other walls of the enclosure 33 are vertical, save that in the wall 39 which separates the pilot from the main burner orifice 0 there is a pocket-like indented portion 40 extending downward approximately to the mid-level of the enclosure 33. The wall 39 has a slanting upper edge cut-out 41 through which an edge 30 of the hood projects angularly. Such hood edge rises slopingly, projecting sufficiently through the cutout 41 to provide a gap 43 through which a tongue of flame may pass. Inasmuch as the gas-air mixture rising from the main burner orifice 0 will spread wideningly into the indented wall portion 40, such tongue of flame will ignite it. Yet such tongue of flame will be protected from lateral gusts of air by the members described, which in effect provide walls for the gap 43. The wall 39 also has a downward-projecting margin 45 held between the burner bracket plate f and the vertical leg 11 of the pilot base bracket 10, these parts being secured by machine screws 46.

The function of the air inflow passage 37 will now be described. When the supply of gas to the pilot 15 is normal the pilot flame will have two substantially equal tongues, one in each of the channel-like portions 29 adjacent to the downward presented edges 30. The ambient air entering the enclosure, as between the lips 34, augmented by air flowing through the horizontal inflow passage 37, will be adequate to support such an equal-forked flame.

However, should the gas supply to the pilot 25 be lessened substantially, the air flowing through the air inflow passage 37 will become a more significant portion of the combustion air. Air so flowing past the thermocouple 14 will not only somewhat cool the thermocouple 14, but will also divert a portion of the available flame from the thermocouple to the tongue which projects through the gap 43 toward the main burner orifice c. This unexpected effect has been verified by repeated observations and tests. By so drawing air through the passage 37 in this manner and so diverting the portion of the flame, ignition of the main burner is favored over the maintenance of the voltage output to the thermocouple 14. Thus ifthe pilot flame lowers further, the drop in the thermocouple output will shut off the gas supply valve before the tongue of flame through the gap 43 has been reduced to a dangerously low level.

It will be understood that the present invention is adapted for use with various types of gas-fired appliances; and for purpose of adaptation, variations in sizes, capacities and proportions will suggest themselves to persons having ordinary skill in the art.

I claim:

1. For use with gas-fired furnaces and like appliances wherein a safety pilot both ignites the gas from a main burner orifice and provides heat to a thermocouple which controls a shut-off valve to such main burner,

a safety pilot comprising a thermocouple supported substantially vertically,

pilot gas supply means including a substantially vertical orifice for gas only, the orifice being spaced from the thermocouple in a substantially vertical plane, and a metal flame-developing hood positioned slantingly above the pilot gas orifice and having downward flanged edges tapering wideningly outward from a central hood indentation, whereby to develop a two-tongued forked flame,

the hood being positioned at such angle to such vertical plane that one of the hood edges directs a tongue of such flame toward the thermocouple and the other edge extends angularly outward,

characterized in having a sheet metal enclosure having substantially vertical side walls, whereby to shield such pilot orifice and at least the lower portions of the hood and thermocouple from horizontal air flow,

one of said side walls extending between the pilot orifice and such main burner and its upper portion being presented beneath such angularly outward extending edge of the hood,-

further characterized in that a horizontal air flow opening extends through that side wall of the enclosure which is adjacent to the thermocouple and remote from the pilot gas orifice,

whereby, if the pilot flame height lowers, inflow of air into the enclosure through said horizontal air flow opening will divert a portion of the flame from that tongue which extends toward the thermocouple to the other tongue which extends over that side wall of the enclosure separating the pilot flame from the main burner,

thereby to prefer ignition of the main burner over voltage output from the thermocouple.

2. A safety pilot as defined inclaim I, wherein the said side wall of the enclosure projects above said outward-extending hood edge and has a cut-out through which said hood edge projects.

3. A safety pilot as defined in claim 1, wherein the said side wall of the enclosure projects above said outward-extending hood edge and has a cut-out through which said hood edge projects, and

said cut-out has a sloping edge substantially corresponding to the slope of said hood edge, and

said enclosure side wall beneath said cut-out comprises a laterally inward indented pocket,

whereby to provide a gap through which may project such tongue of flame to ignite the main burner.

4. A safety pilot as defined in claim 1, wherein the horizontal air flow opening is located at substantially the elevation of that portion of the hood at which flame develops.

5. A safety pilot as defined in claim 4, wherein the enclosure is provided with an upper horizontal lip extending inwardly above said horizontal air flow opening,

whereby to direct inflowing air substantially horizontally toward the thermocouple and impede upward escape of such air.

6. A safety pilot as defined in claim 1,

further having l a bottom for said'sheet metal enclosure, in which the pilot gas orifice, flame-developing hood and thermocouple are mounted,

said bottom being otherwise substantially imperforate, whereby to avoid upward gusts of air through the enclosure.

7. A safety pilot as defined in claim 1, wherein the flame-developing hood has a base portion arising from the pilot gas orifice and open opposite to the thermocouple, and wherein a pedestal shield is provided at substantially the junction of the orifice with the hood, said shield extending substantially horizontally outward from the pilot gas orifice a distance substantially equal to the height thereabove at which the hood develops the flame,

whereby to avoid such upflow of air adjacent to the pilot gas orifice as might so displace the flame upward and extinguish it. 

1. For use with gas-fired furnaces and like appliances wherein a safety pilot both ignites the gas from a main burner orifice and provides heat to a thermocouple which controls a shut-off valve to such main burner, a safety pilot comprising a thermocouple supported substantially vertically, pilot gas supply means including a substantially vertical orifice for gas only, the orifice being spaced from the thermocouple in a substantially vertical plane, and a metal flame-developing hood positioned slantingly above the pilot gas orifice and having downward-flanged edges tapering wideningly outward from a central hood indentation, whereby to develop a two-tongued forked flame, the hood being positioned at such angle to such vertical plane that one of the hood edges directs a tongue of such flame toward the thermocouple and the other edge extends angularly outward, characterized in having a sheet metal enclosure having substantially vertical side walls, whereby to shield such pilot orifice and at least the lower portions of the hood and thermocouple from horizontal air flow, one of said side walls extending between the pilot orifice and such main burner and its upper portion being presented beneath such angularly outward extending edge of the hood, further characterized in that a horizontal air flow opening extends through that side wall of the enclosure which is adjacent to the thermocouple and remote from the pilot gas orifice, whereby, if the pilot flame height lowers, inflow of air into the enclosure through said horizontal air flow opening will divert a portion of the flame from that tongue which extends toward the thermocouple to the other tongue which extends over that side wall of the enclosure separating the pilot flame from the main burner, thereby to prefer ignition of the main burner over voltage output from the thermocouple.
 2. A safety pilot as defined in claim 1, wherein the said side wall of the enclosure projects above said outward-extending hood edge and has a cut-out through which said hood edge projects.
 3. A safety pilot as defined in claim 1, wherein the said side wall of the enclosure projects above said outward-extending hood edge and has a cut-out through which said hood edge projects, and said cut-out has a sloping edge substantially corresponding to the slope of said hood edge, and said enclosure side wall beneath said cut-out comprises a laterally inward indented pocket, whereby to provide a gap through which may project such tongue of flame to ignite the main burner.
 4. A safety pilot as defined in claim 1, wherein the horizontal air flow opening is located at substantially the elevation of that portion of the hood at which flame develops.
 5. A safety pilot as defined in claim 4, wherein the enclosure is provided with an upper horizontal lip extending inwardly above said horizontal air flow opening, whereby to direct inflowing air substantially horizontally toward the thermocouple and impede upward escape of such air.
 6. A safety pilot as defined in claim 1, further having a bottom for said sheet metal enclosure, in which the pilot gas orifice, flame-developing hood and thermocouple are mounted, said bottom being otherwise substantially imperforate, whereby to avoid upward gusts of air through the enclosure.
 7. A safety pilot as defined in claim 1, wherein the flame-developing hood has a base portion arising from the pilot gas orifice and open opposite to the thermocouple, and wherein a pedestal shield is provided at substantially the junction of the orifice with the hood, said shield extending substantially horizontally outward from the pilot gas orifice a distance substantially equal to the height thereabove at which the hood develops the flame, whereby to avoid such upflow of air adjacent to the pilot gas orifice as might so displace the flame upward and extinguish it. 